Assembly And Electrochemical Properties Of Conductive Polymer-based Energy Storage Devices

Conductive polymers have the advantages of high conductivity,low cost,easy preparation,and environmental friendliness,and have great application potential in electrochemical energy storage systems（EES）.However,the expansion and contraction of polymer chains during charge and discharge cycles will cause structural instability and seriously affect the cycle stability,which greatly limits the wide application of conductive polymers in EES.To solve this problem,this thesis improves the structural stability and electrochemical performance of conductive polymers by two strategies:morphology control and construction of composite materials.In the first part of the thesis,polypyrrole nanotubes（PNTs）were prepared by the methyl orange template method.The effects of reactant feeding order on the particle size,morphology,specific surface area,and conductivity of PNTs were investigated.Polydopamine（PDA）in-situ modified PNTs composites（PNT/PDA）were prepared by grinding PNTs and DAH in N-methyl pyrrolidone using the self-polymerization characteristics of dopamine hydrochloride（DAH）under room temperature and light conditions.The electrochemical properties of PNT/PDA were investigated.PNT/PDA‖Mn O₂asymmetric supercapacitor was assembled,and the electrochemical properties of the device were evaluated.The results showed that:（1）During the mixing and grinding process of DAH and PNTs,DAH can polymerize in situ on the surface of PNTs,and the formed hydrochloric acid-doped PNT/PDA can firmly adhere to the carbon cloth current collector to obtain a binder-free electrode.（2）The results of FT-IR and XPS spectra confirmed that the in-situ recombination of PDA and PNTs occurred during the electron transfer from PDA to PNTs,which improved the conductivity of PNTs.The in-situ combination of PDA and PNTs improves the electrochemical structural stability of PNTs.（3）The effect of DAH/PNTs mass ratio on the electrochemical performance of the electrode was investigated.When the mass ratio of PNTs/DAH is 8:1,compared with pure PNTs,the specific capacity is doubled,and the capacity retention rate is increased by 26%after 1000 cycles at 1 A g^-1.（4）The PNT/PDA‖Mn O₂hybrid sodium ion capacitor was assembled with PNT/PDA as the negative electrode and Mn O₂as the positive electrode.The capacity retention rate was83.7%after 10,000 cycles in the current density range of 0.5?5 and back to 0.5 A g^?1,which was higher than 70.5%of the PNT‖Mn O₂sodium ion capacitor.Based on the potential application of two-dimensional（2D）electrode materials in the field of electrochemical energy storage,the second part of the thesis developed a method for the preparation of polyaniline（PANI）nanosheets using anilineate as a precursor,explored the formation mechanism of PANI nanosheets,and investigated its electrochemical performance and potential application in the field of supercapacitors.The results show that:（1）The precipitate formed by aniline and methylene disulfonic acid,sulfuric acid,benzoic acid,oxalic acid,p-toluene sulfonic acid,etc.,under the oxidation of ammonium persulfate（APS）,can be used as a separation-free template for the preparation of polyaniline nanosheets;acids that cannot form precipitates with anilines,such as hydrochloric acid and acetic acid,cannot form PANI nanosheets when coexisting with aniline and APS.（2）The thickness,oxidation state,and electrochemical properties of polyaniline nanosheets can be controlled by controlling the molar ratio of aniline/APS.（3）The electrochemical properties of PANI nanosheets were regulated by adding different concentrations of sodium dodecyl sulfate（SDS）during the synthesis of PANI nanosheets.When the concentration of SDS is 10 cmc,the capacity retention of PANI nanosheets is 56%after 2000 cycles at 1 A g^-1,which is twice that of the initial PANI nanosheets.（4）Symmetrical supercapacitor PANI-SDS-10‖PANI-SDS-10 based on SDS-modified PANI nanosheets has capacity retention of 84%after 4000 cycles at 1 A g^?1.